Process of removing coloring matter from smokeless powder



" Patented Mar. 16, 192s.

UNI-TED STATES 1,571,075 PATENT OFFICE.

EABLE c. rrruan am) sEoneE r. non'rER, or rannm, NEW JEnsEY, assrenons r E. I. no PON'J. DE NEMOURS a com any, or WILMINGTON, DELAWARE, a con- PORATION OI DELAWARE.

PROCESS OF REMOVING GOLORTNG MATTER FROM SMOKELESS POWDER.

1T0 Drawing.

The kind of smokeless owder to which.

15 this invention is particu arly adapted is known either as pyro smokeless powder 'or pyro powder, and may be defined as that grade of smokeless powder made from nitrocellulose almost completely soluble in a mixture of two Ipartsbyi volume of ether to one part of et yl alcohol and having a nitrogen content of about 12.60%. When the World War terminated in the year 1918, there existed large surplus stocks of this pyro powder originally containing about 0.5% of diphenylamine. The principal objections to the use of this powder in arts such as liquid coating compositions and cinematographic films, are (1) its relatively high viscosity, making 'diflicult the preparation of solutions of high solid content, and (2) its dark'color, due to the presence of diphenylamine introduced as a stabilizer, organic impurities (mainly decomposition products 0 the nitrocellulose an nitrodiphenylamines) and inorganic salts (chiefly iron derivatives).

The first of said objections has been overcome by the development of eflicient methods of reducing the viscosity of nitrocellulose solutions, and the second'of the above objections has been overcome in great part by the alcohol extraction process descrlbed and claimed in the patent of R. G. Wood-. bridge, 1,439,656 December 19, 1922, accord ing to which all but faint' traces of the diphenylamine can be renioved from the powder grains. Although the material obtained by said alcohol extraction process answers the requirements for artificial leather coatings, it is not clear enough for use in such compositions as clear pyroxylin lacquer f high nitrocellulose content, c newater or organic solvents, the impurities and Application filed Eovember 20, 1922 Serial 110.602.5130;

matographic film, and transparent or ivory pyralin. 4

We have now discovered that the objectionable color which is perceptible in the above mentioned articles when they are. composed in large part of pyro powder nitrocellulose, can be satisfactoril removed 59 by treating the powder, prefera ly before solution thereof in the ordinaryorganic solvents, with a dilute hydrochloric acid solution containing preferably between 0.05% and of hydrogen chloride. aqueous HCl solution may be used, but an alcoholic HCl solution is preferredz Various other acids capable of transforming the iron derivativesinto soluble compounds can be used Y in place of hydrochloric acid, although hydrochloric acid is-belived to-be best suited for purposes of this invention.

Our complete process in its preferred form comprises, generally speaking, (1) extraction of the diphenylamine with solvents which dissolve it but do'not dissolve the nitrocellulose, (2) treatment of the diphe-o nylamine-free powder with reagents, either acid or alkaline, to render soluble, either in decompositlon products remainingv in the owder, and (3) extraction-of the powder y substances which are solvents for these decomposition products but are not solvents for the nitrocellulose.

Hot denatured alcohol (that is, ethyl alcohol) is the solvent whichywe prefer to use for both steps 1 and 3 supra. The extraction constituting step 3 is preferably performed, in part, concurrently with step ;2 b usin for step 2 hot alcoholic HCl in who the CI content is from about 0.05% to 15%, and preferably 1%.

The pyro powder to be sub'ect to the above-described treatment shoul be in such a physical condition as to expose a large surface, the area of this surface being desirably not less than 1,000 square feet per pound of powder. Thus, if the ain size of the powder available is too arge, .thepowder may be ground (preferably under water or alcohol), or otherwise oomminuted, to such a fineness that it will all pass through a 40- mesh sieve.

Our invention may be illustrated in greater detail by the ollowing example ;-1

(1) One part of pyl'o powder of such fineness as to pass through a 40-mesh sieve is extracted with at least one part, and preferably about two parts, of hot denatured alcohol (i. e. alcohol at a, temperature between about 40 and 70 C.-), the time required for satisfactory extraction of the di phenylamine being usually more than one hour, and preferably about two hours.

(2) The, powder from which diphenylamine has been extracted is then treated with about two parts of hot alcoholic HCl, con- Mining 1% HCl, for at least one hour and preferably for about eight hours.

(3) After draining ofl' the alcoholic HG used in step (2) above, the powder is subjected to further extractions, with hot denatured alcohol as described in step (1) until the extract is practically free from color, about four extractions, each lasting from one to two hours, being ordinarily required.

Where it is necessary to obtain the lightest colored final product, we have found it desirable to include in this process, between steps (1) and (2), a treatment of the powder with aqueous or alcoholic calcium hypochloritesolution.

In the process as outlined above the viscosity of solutions of the powder is reduced almost 7 0%, which is a considerably greater viscosity reduction than is brought about by an equally long treatment with alcohol alone.

Oxalic acid is almost as efiective as hydrochloric acid in solubilizing the insoluble coloring matter in pyro powder, but sulphuric, nitric, and acetic acids, although having some solubilizing action, are far less efieetive than hydrochloric or oxalic acid.

we claim:

1. The process of removing from pyro smokeless powder the coloring matter ordinarily present therein, which comprises subjecting said powder to the action of a dilute acid capable of decomposing insoluble coloring matter into soluble products without injuring the nitrocellulose constituent of the powder, and to the extracting action of a solvent for the resulting soluble decomposition roducts.

9,. Tie process of removing from pyro smokeless powder the coloring matter ordinarily present therein, which comprises extracting said powder with alcohol until most of the diphenylamine present has been removed, subjecting the resulting owder to the action of a dilute acid capa le of decomposing insoluble coloring mattcr into soluble products without injuring the nitro-. cellulose constituent of the powder, and then subjecting the powder to the extracting action of a solvent for the resulting soluble decom osition products.

3. T1e process of removing from pyro smokeless powder the coloring matter'ordinarily present therein, which comprises extracting said powder with alcohol until most of the diphenylamine present has been re moved, subjecting the resulting powder to the action of dilute hydrochloric acid containing between 0.05 and 15% of HCl, and then treating the powder with alcohol to extract therefrom practically all the remaining coloring matter.

4. The process of removing .from pyro smokeless powder the coloring matter ordinarily present therein, WlllCll comprises treating the powder first with hot alcohol to remove dlphcnylamine, then with hot alcohol containing from 0.05 to 15% of hydrogen chloride to render soluble the (:01- oring matter remaining in the powder, and then with hot alcohol to remove the solubilized coloring matter.

5. A process as set forth in claim 1 in which the powder is first ground to such an extent that the surface thereof amounts to at least one thousand'square feet per pound of powder.

6. A process as set forth in claim 4: in which the powder is first ground to such an extent that the surface thereof amounts to at least one thousand square feet per pound oi powder.

7. The process of removing the relatively insoluble coloring matter from yro smokeless powder which is substantial y free from di )henylamine, which comprises treating said powder for at least one hour with hot alcohol containing from .05 to 15% of hydrogen chloride, and then extracting the tofass through a 40-mesh sieve.

n testimony whereof we afiix our signaturcs.

EARLE C. PITMAN. GEORGE F. HUNTER, 

